The present invention relates to a Diesel engine diagnosing device for use in the diagnosis of the operation, and more particularly, in the fuel injection timing of a Diesel engine.
Generally, prior to the examination of a Diesel engine, the fuel injection pump must be disassembled from the Diesel engine body, and the engine body and fuel injection pump must be separately and statically examined by using exclusive examining units. In further detail, the fuel injection pump is usually mounted on to a pump tester equipped with a motor which is used to rotate the fuel injection pump. Various characteristics such as the injection timing, injected fuel amount, etc., of the pump are examined by the pump tester. On the other hand, the engine body is examined only for its operation by using a separate engine tester. In order to known well the status of a Diesel engine, however, it is desirable for various dynamic operations of the engine to be examined under the condition where the Diesel engine body and the fuel injection pump are assembled together. To this end, a timing device, for example, disclosed in the Japanese Patent Publication No. Sho-47-29621, is used. Because such a timing device requires an electrical signal corresponding to the change of injection pressure occurring in the fuel injection system of a Diesel engine, and a top dead center signal representative of the top dead center position of said engine, the construction of a prior-art device of this type becomes very complex. Moreover, it is difficult for the prior-art device to provide an accurate measurement because the signal occurring due to the secondary injection pressure and/or the change of the number of revolutions of the engine tends to cause erroneous measurements.